I was one of the mgrs of the engine line at Cox when Roy still owned it, and until Leisure Dynamics "flew" the company into the ground. I worked closely with R&D and QC.

I know, I just dated myself.

In the test cells, there was a lot of alternative oils tested, and alternative fuels. The reset tool was essential. If the ball socket comes loose, it's a matter of time until failure. The pistons are a copper alloy, plated with chrome. They are soft and malleable. Ensure the piston reset tool is used on a known flat surface, or you may find that the piston itself has been distorted. And the more times you reset the ball-socket, the softer the socket becomes, and the more often it needs reset. It's certainly a catch 22.

Synthetic oils have been used successfully, but with premature wear on the crankcase/crankshaft bushing, and on the top end of the connecting rod. I have personally turned the engines in the test cells > 35,000 rpm (you read me right). On castor, the engines suffered no damage. On synthetic, the engine would heat-seize mid-run with the result that parts went all over the place.

Push them into 35 - 50k rpm range, and the glow plug packing material fails.

We did test some engine mods that worked. This only works in a non-throttled setting. If you want to "spook up" the .049 on a reed valve engine, remove the reed and carefully drill out the air intake to 0.062". Fabricate a replacement reed from 0.010" mylar.
This mod will take an engine turning a 6x3 @ 16k to about 18.5k. This mod will NOT allow the engine to be throttled down with the cylinder sleeves. It can't maintain enough low pressure to keep fuel flowing when throttled back.

The other item we used to do is to position the cylinder so that the transfer ports of the cylinder were on the sides of the engine and not located fore/aft. This allows the crankshaft to provide a little centrifical force to the fuel/air charge and you'll gain another 500 rpm. CAUTION: do NOT shave more off the cylinder to accomplish this than 1/4 of a turn of the cylinder. If you do, you'll adversely affect the piston's location in the cylinder, overly raise the compression ratio, and in worse case cause piston/cylinder interference. This mod works on the TeeDee engines as well as the reeded engines.

To cut the crankcase down to accomplish moving the ports to the sides....use a known flat surface (glass) and lapping compound. Go slow.....Once you are done, it's likely that the top of the C'Case is NOT perfectly flat anymore, thus compromising the cylinder seal. Use Loctite Blue (medium strength) to both seal and hold the cylinder into place when you reassemble.


Hope this helps,


Dave Babb
Former Cox employee.